One of the most important milestones in the wireless communications is the arrival of third generation or 3G technology and devices that are capable of transferring voice and data at much higher speed. One new development in mobile device technology is the use of Internet Protocol (IP) addresses to identify and communicate with mobile devices. However, using IP addresses to identify and communicate with a mobile device brings some unresolved issues. For example, carriers responsible for the communication to and from the mobile devices may change the IP address assignment frequently and arbitrarily. Different carriers may also have different policies regarding the frequency and manner of assigning the IP addresses. Therefore, it is unknown, at any moment, what is the current IP address of the mobile devices.